Quadrantal compensator



Dec. 7, 1943. w. P. LEAR- 2,336,361

QUADRANTAL COMPENSATOR Filed. July 11, 1940 2 Sheets-Sheet 1 INVENTOR.

M Q M V ATTORNEY.

FIG

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TO LOOP ANTENNA Dec. 7, 1943. w, R LEAR 2,336,361

QUADRANTAL COMPENSATOR Filed July 11, 1940 2 Sheets-Sheet 2 3 Hull;

To LOOP ANTENNA Patented cc. 7, 1943 William P. Lear, Dayton, Ohio, assignor, by mesne assignments, to Lear Avia, Inc., Piqua, Ohio, a corporation of Illinois 6 Claims. This invention relates to quadrantal corrector mechanisms for effecting bearing compensations in radio direction indicator systems. The present case is a continuation-in-part of my copending application, Serial No. 311,313, filed December 28, 1939,..which issued on September 22, 1942, as Patent No. 2,296,285, and assigned to the same assignee.

In accordancewith the present invention, I provide improvedconstructions for quadrantal error compensation of indications of a radio direction finder.,,fI 'he system of the invention is particularly applicable to automatic direction finders operable over 360 of arc, such as disclosed in my copjending application, Serial No.

286,733, filed onfJuly 27, 1939, which issued on January 19, 1943 as Patent No. 2,308,521. Means are provided to quickly convert the corrector mechanism for different radio frequency bands of operation, enabling a busy pilot of an aircraft to readily efiect a change. The mechanism comprises linked arms provided with at novel spring arrangement insuring uniform pressure between the corrector cam and cam follower throughout their 360- of operation despite movement between the minimum and maximum degrees of compensation, or wear. Th cam blank is inscribed with apredetermined aphic representationpermitting direct calibration and simple construction of *the compensator cam for the mechanism.

It is accordinglyan object of my present in vention to provideja novel bearing compensator niiechanism for a radio direction finder installat On.

Another object of the invention is to provide a quadrantal error. corrector with readily replaceable cam means for quickly converting the sys tem to any one of plurality of ranges of radio operation. 7 II Still another object of the present invention is to provide a novel quadrantal error corrector arrangement with substantially uniform camfollower pressure throughoutits 360" of operation and range of compensation.

A further object of the invention is to provide a novel compensator mechanism comprising linked arms with a spring biasing arrangement exerting uniform radial pressure over wide degrees of compensation.

Still a further object of the invention is to provide a corrector cam blank inscribed with predetermined graphic representations for effecting direct quadrantalerror compensation calibratlon. I

Application July 11, 1940, Serial No. 344,854

These and other objects of the present invention will become moreapparent in the following description of a specific embodiment thereof illustrated in the accompanying drawings, in which:

Fig. 1 is a plan view, partially broken away, of the quadrantal error corrector, embodiment with its cover open.

Fig. 2 is a vertical cross-sectional view through the corrector, with the cover closed, corresponding to a line 2-2 taken along Fig. 1.

Fig. 3 is an enlarged perspective illustration of details comprising the compensator mechanism.

Fig. 4 is a plan view of the inscribed quadrantal error corrector cam blank.

The compensator embodiment chosen to illustrate the present invention is arranged for coupling between a rotatable directional or loop antenna and the direction or bearing indicator. The compensator renders the bearing indications correct throughout the 360 of operation of the directional antenna. By employing the compensator or corrector in an automatic direction finder system, direct bearing indicationsare obtained, eliminating interpolation or calculation. The compensator of the present invention may well be used in the automatic radio direction indicator disclosed in my Patent No. 2,308,521, referred to above. The quadrantal error corrector schematically indicated in Figs. 7, 8 and 9 therein may well be the compensator of the present invention. As is known by those skilled in the art, non-symmetry of metallic objects surrounding the rotatable directional antenna results in the quadrantal errors to be compensated for. The calibration of the compensator depend upon the physical characteristics, particular installation, and the frequency range of the radio reception.

The-quadrantal error corrector of the invention is designed as a unitary structure enclosed in a housing 10 having a lid ll hinged at 12, and attached by screws I to base I 5. The compensation mechanism is coupled to shaft I6 of th directional or .loop antenna- (not shown), through an opening in base l5, ,The .loop antenna may be mountedbeneath or. above the corrector mechanism, in accordancewith the installation requirements. When mounted above, the corrector is turned about from the position illustrated. Loop shaft I5 is coupled to rod ll of the corrector through flexible coupling unit l8. Coupling I8 comprises flexible disks l9 spaced by washers 20 and secured together by rivets 2|. Small axial misalignments encountered between the corrector tion orotherwise, accordingly do not afiect the calibration or operation of the system. A flexanism, otherwise projecting screw 44 prevent. its ible cable 22 is coupled to the corrector mechaflnalinsertion. Access to cam II is readily afnism for connection to the bearing indicator, not forded by opening lid H through thumb screw shown. 42 operating on element 42 arranged to be drawn A feature of the present invention is the asagainst the adjacent edge of housing ll. sembiy of the compensator, motive drive therefor, Cam 30, cam supporting members 4|, and linked and coupling gearing into a unitary arrangetrolley 32 to 28 of the quadrantal error corrector ment. As shown in Fig. 1, a reversible electric mechanism, are upported on a shelf 44 arranged motor 22 is contained within the compensator above central supporting structure 2!. Horizonstructure, coupled to horizontal rod 24 thereof tal drive rod 24, directly coupled to motor 22 as through reduction gearing 2t, 2t and magnetic previously described, is rotatably supported in clutch 21. Reversible motor 23 and magnetic structure 28. A horizontal shelf 45 is arranged clutch 21 are interconnected to the radio direcbeneath shaft 24, and held against the horizon. tion finder control system through electric cable tal section of structure 22 by a nut 48 threaded 22'. Preferred arrangement and connections for 1 on an extension of sleeve 41 concentric about the motor, clutch and drive are disclosed in the corrector shaft II. An assembly is provided for Patent No. 2,308,521. With this arrangement, the holding the mechanism above shelf 4|, in operamotor and clutch are electrically shielded from tive and in 360 rotational condition. A nut the exterior by metallic housing I I as well as the member 42 rests between the unpivoted end of internal metallic supporting structure 22. Radio link 2 above shelf 44; and the hub of worm gear interference waves caused by the operation and- '52 below shelf 44, proj in t rou h an opening interruptions of the motor and clutch are reduced therein. in intensity or otherwise prevented f b ing A worm is is secured to horizontal shaft 24 and picked-up by the radio antennae. Base-ll is Y coacts with a worm gear II secured to atubular preferably metallic t e-t radio lu -1 as shaft or sleeve I1 directly concentric about shaft of t enclosed l t i mar hriv 1' l1 and connected with link 3'. Shaft l1 and Quadrantal error compensation is eifected by. sleeve I! thereabout are freely rotatable with r imparting predetermined I relative-angular dis:- 5 spect to each other, and are respectively coupled bursementsbetween loop shaft is and-indicator to linked trolley 33-" and worm gear drive 4!, shaft 22 as determined bya' cam.2l."- 82- in a manner to be more fully'described in The effective 'cam surface it of ll 'co'acts connection withFig. 3; Indicator cable 22 is rewith its cam follower l2, radially spring'biased movably coupled to corrector shaft 24 bycoupling by a trolley composed of linked farms, u, ll, v piece ii. up i g e ement 52 is arranged at a. The-quadrantal error compensator-cr me in the opposite end of shaft 24 in the event that a vention, including the interna1-. m; nd trolley '35.. second'indicator is to be coupled thereto, or that amhgemeht,'-correspohdg t t -teem? di t; couplingfis desired from that end of the unit. closed in my Patent No."-,v2,296,285. referredto; A sb cck 53 i attached tohouslng ll about above. Details of design, construction and ad-z: cable 22,

vantages thereof, will be described inmore'de- 5- Fig. 3 man enlarged perspective view diagramtail hereinafter in connection with Pig. 3. "40 imfltically illustrating the preferred arrangement 15m the quadrantal error corrector mechanism of the invention. Cam follower 22 is securedly tor cam ll. Since modern radio-direction finders ih 0!! link "of e r lley to keep its cmare operable on several radio communication flct"D in't v at a predetermined relative disbands, and the effective calibration of the cam, ositi n w th respect to the trolley m- Cam is different for widely separated bands, a i l er 31 is P f ra ly made ofmaterial havchange is preferable for accurate results. When. 1 8; W r ist nt qualities and low sliding fricthe direction finder is used aboard h t, -tion coemcient on metallic cam surface 2|, such a quick and positive change-over of the cam is I as of fine fibre 0 r phite impregnated Bakelite. important when indicated. In accordance with i 35 r pivct'ally linked together. the invention, the Outer periphery of th cm Screw members 5i are indicated for linking the rests against spaced washers I1, 21 having overarms and holding them st ly t her. Howlapping raised ends. A spring clip 82 presses every other suitable m ns may be used. End against straight edge as on the side of cam 80, of link 33 c ntains an opening w i h l se y opposite washers 31 3' up a projects over bl flts onto the top end of central shaft II. End the top surface of cam 2| to hold the cam down link 33 is 8diustably se u ed to shaft II within coacting recesses in its supporting strucby means of a s iti d en 54 e n in t i p ture 4|. A screw or other suitable projection ting with shaft i1 and a screw 5! threadis arranged in cam 30, coacting with a hole in ed nto the resultant end parts 58, 56. Screw one of the cam supporting member, 4 t g 55 preferably projects somewhat from link II determine the position of cm a 7 and has a knurled head, to permit convenient ac.

c 0 is accordingly readily removed f om cess thereto and manipulation thereof for anthe structure by simply pressing clip 28 outward- S y adjusting link 33 on shaft l'l. 1y, raising the adjacent cam edge 39 upwardly, The uhpivoicd e d of link 3 is si ila ly seand then sliding it out from under overlying a cured t0 the tubular shaft concentric about edges of washers 31, 21. A new cam may thus shaft The p it end 58;" of link 38 is enbe quickly substituted by sliding it under the gaged by screw 59 to grip the to ndcf sleeve projecting edges of washer 31, 31, r s i cam 51. Sleeve 51 and shaft I! are freely relatively follower 32 inwards radially, and moving the cam n rly displa es-hie with respect to each other. edge (corresponding to 39 of cam 30) under clip 10 r a iven setting of links. and 38 on shafts ;g The muhded projection of u 3; permits i I and 51, the relative angular displacement bethe cam edge to be pressed down against it, tween these shafts depends upon the radial posi- An important feature of the present invention resides in the ready replaceability'of the correc whereupon spring 32 moves to hold the cam in tion of cam contact 32 as controlled by cam sur its ilnal level position. The cam is necessarily face II of cam 30. Calibrated variation of the fitted in proper relation with respecttothe mechll radial extension of cam follower 32, cam con trolled in accordance with its angular position, effects the quadrantal error compensation desired.

Central shaft l1 and link 33 of the trolley are in direct connection with the loop antenna, and rotate therewith without angular disparity. Sleeve 51 and link 36 of the trolley are in direct mechanical coupling with indicator shaft 22 extending to the azimuthal indicator of the System.

either direction, in accordance with the actuation of loop motor 23 under the control of the automatic direction finder. The indicator cable 22 is directly coupled to the compensator shaft 24, and therethrough to link 36 of the trolley.

Fig. 4 illustrates the cam blank used in constructing the corrector cam 30. The cam blank 30 is similar to that disclosed in my Patent No. 2,296,285 referred to above. The cam blank has inscribed thereon a 360 graph designed to translate the quadrantal error determinations on the direction finder installation by a direct, accurate and simple manner. A series of concentric circles 65 correspond to the magnitude of the quadrantal error, in degrees, as determined by experiment in the usual manner. The centrally disposed circle 66, labeled 0," corresponds to zero quadrantal error correction. The concentric circles radially larger than zero circle 66, refer to a negative quadrantal error correction; the smaller circles, to a positive quadrantal correction, as indicated in Fig. 4. Concentric circles 65 are shown spaced apart corresponding to two degree corrections. Other spacings are however feasible. Ready interpolation may be effected therebetween.

Arcuate radial lines 61 are arranged at spacings over the 360 of arc. The arced calibration lines 61. are designed in accordance with the geometrical law of motion and coaction of cam contact 32 with respect to cam surface 3|, which primarily depends upon the design, dimensions and arrangement of linked trolley 33-38. The curvature of lines 61 may be determined mathematically or empirically as preferred, to effect the respective positive and negative compensations. rectly inscribed on cam blank 30', such as by printing, etching or the like, calibration of the cam may quickly follow from the quadrantal error determinations for the installation. The azimuthal scale on cam blank 30' of Fig. 4 reads ascending in the counter-clockwise direction since the particular cam is inserted face down in the corrector of Figs. 1 and 2. Due to set screw 40, the cam is insertable in the corrector in only one position, the proper one.

The quadrantal error compensation curve is plotted on the chart of cam blank 30'. In practice, the quadrantal error compensation determinations are preferably taken for each 10 of arc, and correspondingly plotted along spaced arcuate calibration lines 61 and circles 65. The smooth continuous curve connecting these points is thereupon determined on blank 30'. The cam With the graphic calibration chart di-.

blank is then suitably out to derive internal calibrated cam 30. Cam edge 3| is smoothed to assure its smooth frictional 'engagement with contact point 52' of cam follower 32. When contact 52' is pressed inwards radially with respect to the mean or zero correction position of circle 68, links 33 and 38 are diverged, causing a corresponding increase in the angular relation between shafts l1 and 51. The resultant action may be viewed as a correspondingly increased (clockwise) indicator reading for a given orientation of the loop antenna. Conversely, when contact 52' is permitted to move outwards radially, the angular relation of shafts I1 and 51 is decreased from the predetermined normal, effecting a virtual decreased (counter-clockwise) indicator reading. Complete and,v accurate quadrantal error compensation oven-the 360 azimuth may be thus effected with thesystem of the invention, which compensation is automatically and continuously present for all indications.

An important feature of the invention is the insurance of substantially uniform pressure of cam contact 52' on the cam and avoidance of back-lash despite wide radial displacements of the trolley or of wear. Towards this end I.provide spring 10 in the trolleyto effect the continuous mechanical biasing radially outwardly of cam follower 32, arranged with respect to linlm 33-36 in a novel and advantageous manner. One end of spring 10 is anchored in link 34 at a predeterminedly locatedjhole ll therein. The other end of spring 10 is anchoredin hole 12 of opposite link as. The inside portion is off-link 36, near its pivotal joint 5| with link 35, is undercut to permit the associated end of spring I0 to ride under link 35 at reduced angles between links 35 and 36. 1

Through extensive determinations, I have found that the above described arrangement of spring 10 in the four arm trolley 33-46, affords a substantially uniform pressure for radially biased contact point 52 against cam surface 3|. The uniform cam contact pressure is present throughout the relatively wide radial displacement of the trolley system despite usual wear in the respective components of the compensator unit, and provides negligible backlash in the system. The substantially uniform cam follower pressure and negligible backlash of the preferred arrangement occurs in the range between the minimum and maximum compensation positions of the system.

The principle of the preferred arrangement of biasing spring 10 with respect to the four trolley links 33-36 is to anchor one end of the spring very close to an intermediate pivot 5|, (such as between links 35 and 36), and to anchor the other end of the spring at an intermediate portion of an opposite link (such as'link 34), at a position near the pivot diagonally opposite the first mentioned one. Thus, one anchor of spring 10 is at hole 12, with undercutting l3 affording an anchorage as close to pivot 5| between links 35, 36 as is practicable; the opposite anchor for spring 10 being at II on link 34. The choice of anchor position 1| on link 34 is somewhat critical to give the substantially uniform cam contact pressure condition. The actual location of point H is preferably determined empirically. In experimental determinations, the location of anchor point II on a link corresponding to 34 was in the range of 20 to 40 percent of the length of link 34 from the pivot 5| between arms 33 and 34. Spring I0 is under tension.

Although! have disclosed preferred arrangements for carrying out the principles of my present invention, I am aware that modifications falling within the broader spirit and scope .thereof are feasible, and accordingly I do not intend to be limited except as set forth in the following claims.

What I claim is:

1. In a quadrantal error corrector having an internally calibrated cam surface, a shaft, a sleeve concentric with said shaft, mechanism coupling said sleeve and shaft for predeterminedly controlling their relative angular displacement while permitting rotation thereof including a cam follower for coacting with the internal cam surface, a trolley forming a closed linked arrangement and carrying said cam follower, the unpivoted ends of said trolley being respectively secured to the ends of said shaft and sleeve, and a spring normally biasing said cam follower radially outwards against the cam surface, a gear secured to said sleeve, and an indicator shaft geared to said gear.

2. In a quadrantal error corrector having an internally calibrated cam surface, a shaft, a sleeve concentric with said shaft, mechanism coupling said sleeve and shaft for predeterminedly controlling their relative angular displacement over 360 of arc while permitting rotation thereof including a cam follower for coacting with the internal cam surface, a first link engaged with said shaft, a second link engaged with said sleeve, elements joining said first and second links and carrying said cam follower, and a spring for normally biasing said cam follower radially outwardagainst said cam surface, said spring being anchored on said elements and said.

ing corresponding portions of the outer periphery of said cam plate, an index projection on said cam, and a spring clip fastened on said frame for snapping against to the outer periphery of said cam plate when said index projection is in a predetermined opening of said frame to stably hold said cam in said recess.

4. In a quadrantal error corrector a shaft,- a sleeve concentric with said shaft, mechanism coupling said sleeve and shaft for'predeterminedly controlling their relative angular dis-- placement over 360 of are while permitting rotation thereof including a cam follower for coacting with an internal cam surface, a first link engaged with said sleeve, a second link engaged with said shaft, a third and fourth link respectively interlinking with said first and second links and carrying said cam follower, and a spring anchoredbetween the end of said first link which joins said third link and an intermediate portion of said fourth link in a manner to provide substantially uniform pressure of said cam follower against said internal cam throughout a relatively wide compensation range, said first link end being undercut at the spring anchor position to permit said third link to freely pivot thereover.

5. In a quadrantal error corrector a first and second shaft, mechanism coupling said shafts for predeterminedly controlling their relative angular displacement over 360 of arc while permitting rotation thereof including a cam follower for coacting with an internal radially calibrated cam surface, a first link engaged with said first shaft, a second link engaged with said second shaft, a third and fourth link respectively interlinking with said first and second links and carrying said cam follower, and a tension spring anchored between the end of said first link which joins said third link and an intermediate portion of said fourth link located at a distance in the range of 20 to 40 percent of the fourth link length fromits connection to said second link in a manner to provide substantially uniform pressure of said cam follower on said internal cam throughout a relatively wide compensation range.

6. In a quadrantal error corrector having an internally calibrated cam surface, a shaft, a sleeve concentric with said shaft, mechanism coupling said sleeve and shaft for predeterminedly controlling their relative angular displacement while permitting rotation thereof including a cam follower for coacting with the internal cam surface, a trolley forming a closed linked arrangement and'carrying said cam follower, the unpivoted ends of said trolley being respectively adjustably secured to the ends of said shaft and sleeve, and a spring normally biasing said cam follower radially outwards against the cam surface, a gear secured to said sleeve. and an indicator shaft geared to said gear.

WILLIAM P. LEAR. 

